A coupling assembly for rotatably coupling two shafts comprises a first shaft extending longitudinally between a first end and a second end and having a radially extending flange at said second end; a second shaft extending longitudinally between a first end and a second end and having a radially extending hollow receiving member at said first end, the flange being positioned within the hollow receiving member, The hollow receiving member comprises an inner cylindrical surface comprising at least one longitudinally extending member groove and the flange comprises an outer cylindrical surface comprising at least one longitudinally extending flange groove, The coupling assembly also includes a barrel-shaped roller bearing provided to extend longitudinally within and in contact with both said flange groove and said receiving member groove and the flange groove and/or said member groove has a longitudinal concave barrel shape for receiving and contacting said barrel shaped roller bearing.
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7. A method of rotatably coupling two shafts, the method comprising the steps of:
providing a first shaft extending longitudinally between a first end and a second end and having a radially extending flange at said second end; and forming a longitudinally-extending flange groove in said radially extending flange;
providing a second shaft extending longitudinally between a first end and a second end and having a radially extending hollow receiving member at said first end; and forming a longitudinally-extending member groove in an inner circumferential surface of said hollow cylindrical member;
positioning said flange within said hollow receiving member; and further providing a barrel-shaped roller bearing that extends longitudinally within, and is in contact with, both said flange groove and said receiving member groove and
further wherein said flange groove and/or said member groove has a longitudinal concave barrel shape for receiving and contacting said barrel shaped roller bearing.
1. A coupling assembly for rotatably coupling two shafts, the coupling assembly comprising:
a first shaft extending longitudinally between a first end and a second end and having a radially extending flange at said second end;
a second shaft extending longitudinally between a first end and a second end and having a radially extending hollow receiving member at said first end,
the flange being positioned within the hollow receiving member; and
wherein said hollow receiving member comprises an inner cylindrical surface comprising at least one longitudinally extending member groove; and
wherein said flange comprises an outer cylindrical surface comprising at least one longitudinally extending flange groove;
said coupling assembly further comprising a barrel-shaped roller bearing provided to extend longitudinally within and in contact with both said flange groove and said receiving member groove and further wherein said flange groove and/or said member groove has a longitudinal concave barrel shape for receiving and contacting said barrel shaped roller bearing.
2. The coupling assembly according to
wherein the barrel-shaped roller bearing has a larger radius at a mid-point of the barrel along the longitudinal direction compared to a radius at either end of the barrel-shaped roller bearing.
3. The coupling assembly according to
4. The coupling assembly according to
5. The coupling assembly according to
6. The coupling assembly of
8. The method of
securing the flange within the hollow cylindrical member such that the first shaft extends out of the hollow cylindrical member through a hole in a first surface of the hollow cylindrical member.
9. The method according to
wherein the barrel-shaped roller bearing has a larger radius at a mid-point of the barrel along the longitudinal direction compared to a radius at either end of the barrel-shaped roller bearing.
10. The method according to
11. The method according to
12. The method according to
13. The method of
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This application claims priority to European Patent Application No. 17461568.2 filed Jul. 18, 2017, the entire contents of which is incorporated herein by reference.
The present disclosure relates to coupling assemblies for rotating shafts. In particular, the disclosure relates to coupling assemblies for torque transmission systems.
In many mechanical situations, it is desirable to connect two coaxial shafts such that torque is transmitted from one shaft to the other via rotation while also being able to accommodate axial misalignment between the two shafts.
U.S. Pat. No. 4,464,141 describes a shaft coupling system for accommodating axial displacement and angular misalignment between two shafts. These couplings may be used to allow the transmission of power between a drive shaft and a driven shaft. In this system, a spline adapter, connected to a first shaft, cooperates with a bushing, connected to a second shaft, that has spline teeth extending from its outer surface. The spline teeth are substantially boat-shaped. The shape of the teeth allows for extra clearance at the ends of the coupling system, which is necessary to accommodate angular misalignment between the shafts. However, the boat shape of the teeth can be difficult to manufacture.
Another known flexible coupling is described in U.S. Pat. No. 2,375,030. In this universal coupling a first shaft has a head at one end, the head having a part cylindrical surface. The head fits within the interior of a sleeve that is rigidly connected to a second shaft. The radially outer surface of the head has a plurality of longitudinally extending semi-cylindrical grooves spaced around its circumference. The grooves are oriented in a direction parallel to the shaft axis of the first shaft. The sleeve also has a plurality of longitudinally extending semi-cylindrical grooves on its inner surface which are complementary to the grooves of the head.
A roller is inserted into each cylindrical aperture defined by the complementary semi-cylindrical grooves, to serve as a torque transmitting key between the flange and the hollow cylindrical member without interfering with a rocking motion between head and sleeve during misalignment of the shafts. When torque is applied to the first shaft, the torque is transmitted from the shaft to the flange, from the flange to the roller, from the roller to the hollow cylindrical member, and from the hollow cylindrical member to the second shaft.
It is desirable to improve such flexible couplings, for example, by reducing the manufacturing time and/or costs, improving the torque transfer between the shaft (i.e. reducing frictional losses in the flexible coupling), and/or reducing backlash between the two shafts and the present disclosure addresses these issues.
According to a first aspect, the disclosure provides a new type of coupling assembly for rotatably coupling two shafts, the coupling assembly comprising: a first shaft extending longitudinally between a first end and a second end and having a radially extending flange at said second end; a second shaft extending longitudinally between a first end and a second end and having a radially extending hollow receiving member at said first end, the flange being positioned within the hollow receiving member; and wherein said hollow receiving member comprises an inner cylindrical surface comprising at least one longitudinally extending member groove; and wherein said flange comprises an outer cylindrical surface comprising at least one longitudinally extending flange groove; said coupling assembly further comprising a barrel-shaped roller bearing provided to extend longitudinally within and in contact with both said flange groove and said receiving member groove and further wherein said flange groove and/or said member groove has a longitudinal concave barrel shape for receiving and contacting said barrel shaped roller bearing.
A method of rotatably coupling two shafts is also described herein, the method comprising the steps of providing a first shaft extending longitudinally between a first end and a second end and having a radially extending flange at said second end; and forming a longitudinally-extending flange groove in said radially extending flange; providing a second shaft extending longitudinally between a first end and a second end and having a radially extending hollow receiving member at said first end; and forming a longitudinally-extending member groove in an inner circumferential surface of said hollow cylindrical member; positioning said flange within said hollow receiving member; and further providing a barrel-shaped roller bearing that extends longitudinally within, and is in contact with, both said flange groove and said receiving member groove and further wherein said flange groove and/or said member groove has a longitudinal concave barrel shape for receiving and contacting said barrel shaped roller bearing.
The method may further comprise the step of securing the flange within the hollow cylindrical member such that the first shaft extends out of the hollow cylindrical member through a hole in a first surface of the hollow cylindrical member.
In any of the examples of the coupling assembly and method described herein, the roller bearing may have an axis of circular symmetry defining a longitudinal direction, and the barrel-shaped roller bearing may have a larger radius at a mid-point of the barrel along the longitudinal direction compared to a radius at either end of the barrel-shaped roller bearing.
In any of the examples of the coupling assembly and method described herein, the flange groove and the member groove may each have a concave surface in the circumferential direction.
In any of the examples of the coupling assembly and method described herein, the radius of curvature of the concave surface in the circumferential direction may be equal to or larger than the largest radius of the barrel-shaped roller bearing.
In any of the examples of the coupling assembly and method described herein, the concave surface, or each concave surface has a radius of curvature in the longitudinal direction that is less than infinity and is equal to or greater than a longitudinal radius of curvature of the roller bearing.
In other words, wherein a radius of curvature equals infinity, the surface is flat.
In any of the examples of the coupling assembly and method described herein the radius of curvature in the longitudinal direction may be between 8 times and 10 times larger than the longitudinal radius of curvature of the roller bearing. Having a larger radius of curvature prevents edge chopping.
Having a curved groove in the longitudinal direction improves the torque transfer between the two shafts.
Roller bearings made with this shape are commercially available with high hardness, very smooth surfaces (surface roughness, Ra, less than 0.16 μm), and low cost.
Having the roller bearing fit in circumferential curved grooves improves the torque transfer and reduces pressure points that would result from, e.g. flat (radially extending) sides of the grooves. This results in better torque transfer. In the preferred range, this feature prevents edge chipping by giving a small amount of clearance at the edges.
Certain embodiments of the present disclosure will now be described in greater detail by way of example only and with reference to the accompanying figures in which:
As shown in
The regions on the outer circumferential surface 36 of the flange 30, between the grooves 32, may be curved convexly, with a respective radius of curvature, in both the circumferential and longitudinal directions. The radius of curvature in the longitudinal direction will usually be larger than the radius of curvature in the circumferential direction.
As shown in
In some examples, the second shaft 50 may also have a radially extending flange 58 at its second end 52, i.e. at the end opposite end from a hollow cylindrical member 54, for connecting the second shaft 50 to another item. Alternative connectors, such as splines, may be used instead of the flange 58 on the second shaft 50.
The hollow cylindrical member 54 has a first side 541 and an opposing second side 542 with the cylindrical outer surface 543 extending therebetween. As is shown in
In some examples, the second side 542 of the hollow cylindrical member 54 may comprise a plate 57 having the hole 57a therethrough and the plate may be connected to the hollow cylindrical member 54 via screws 59. Alternatively, the plate 57 could be in the form of a cup (not shown) having an internal screw thread around the rim that mates with a screw thread on the external surface 543 of the hollow cylindrical member 54. The plate 57 could then be screwed onto the hollow cylindrical member 54. Other methods or means of forming this hollow cylindrical member 54 may also be used.
The hollow cylindrical member 54 therefore defines an enclosure suitable for containing the radially extending flange 30 of the first shaft 20 therein. The first shaft 20 may then extend through the hole 57a and connect to another member via splines 22. Alternative connectors are also envisaged instead of the splines 22.
As shown in
Barrel shaped roller bearings 40 are then positioned to extend longitudinally within and in contact with these grooves as shown in
As shown in
In some embodiments, the grooves 56 in the hollow cylindrical member 54 have a semi-cylindrical shape in the longitudinal direction. That is, the shape of these grooves 56 may be defined by the intersection of a cylinder with the inner surface of the hollow cylindrical member 54. This means that the sides of each groove 56 extending in the longitudinal direction (i.e. parallel to the second shaft axis Y) are flat, as depicted in
In the longitudinal direction, the grooves 32 in the flange 30 are not flat but are curved, as shown in the cross-section of
Alternatively, the curve of the flange groove 32 may have a larger radius of curvature R1′ in the longitudinal direction than the (longitudinal) radius of curvature R1 of the roller bearing 40. For example, the longitudinal radius of curvature R1 of the groove 32 may be up to 100% larger than the longitudinal radius of curvature R1 of the roller bearing 40.
As shown in
The flange 30 has a longitudinal width 30a (i.e. the width between first 34 and second 35 sides of the flange 30) that is smaller than the longitudinal internal width 54a of the hollow cylindrical member 54 in which is it positioned. Optionally, the roller bearings 40 have a length 40a that is substantially the same as or equal to the width 30a of the flange 30. Thus, in the neutral position, there is a clearance between the axial sides 34, 35 of the flange in the longitudinal direction, and the sides of the enclosure around the flange 30. This clearance allows the flange 30 limited movement inside the enclosure, such as may result from axial misalignment between the first 20 and second shafts 50.
When torque is applied to the first shaft 20 about the first shaft axis X, the flange 30 transfers the torque to the roller bearings 40 sitting within their respective flange grooves 32. The roller bearings 40, in turn, bear against the grooves 56 of the hollow cylindrical member 54 and thus transmit torque thereinto. As described above, the hollow cylindrical member 54 is fixedly attached to (or formed integrally with) the second shaft 50 and thus the torque is transmitted into the second shaft 50 causing it to rotate about the second shaft axis Y. Of course, the same process works in reverse, in that torque applied to the second shaft 50 about the second shaft axis Y is transmitted into the hollow cylindrical member, into the roller bearings 40, into the flange 30, and into the first shaft 20.
As shown in
In an alternative example, not shown, the grooves 32 of the flange 30 may be flat in the longitudinal direction and the grooves 56 of the hollow cylindrical member 54 may be curved in the longitudinal direction in the manner described above for the flange grooves 32. This arrangement may provide the same advantages as having the longitudinally curved grooves on the flange, as described above.
In another alternative example, not shown, the grooves 32 of the flange and the grooves 56 of the hollow cylindrical member 54 may both be curved in the longitudinal direction in the manner described above for the flange grooves 32. This exemplary flexible coupling 10 requires that the hollow cylindrical member 54 be made from at least from two separate pieces, so that the rollers 40 may be inserted into the grooves 32, 56 between the flange 30 and hollow cylindrical member 54.
Trybuła, Daniel, Sobieszek, Maciej
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Aug 02 2017 | SOBIESZEK, MACIEJ | HS WROCLAW SP Z O O | ASSIGNMENT OF ASSIGNORS INTEREST SEE DOCUMENT FOR DETAILS | 045775 | /0505 | |
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